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Seasonal affective disorder



Seasonal affective disorder (SAD) refers to episodes of depression that occur every year during fall or winter. Symptoms improve in spring and summer.

Alternative Names

Depression - winter; SAD


The disorder may begin in adolescence or early adulthood. Like other forms of depression, it occurs more often in women than in men.

Most people with the "winter blahs" or "cabin fever" do not have SAD. People who live in places with long winter nights are not necessarily more likely to have SAD.

The cause of SAD is not known, but it is thought to be related to many factors, including:

  • Ambient light
  • Body temperature
  • Hormone regulation

A rare form occurs in the summer.


Symptoms usually build up gradually in the late autumn and winter months.

  • Afternoon slumps with decreased energy and concentration
  • Increased appetite with weight gain (weight loss is more typical of other forms of depression)
  • Increased sleep and excessive daytime sleepiness (problems sleeping are more typical of other forms of depression)
  • Lack of energy and loss of interest in work or other activities
  • Slow, sluggish, lethargic movement
  • Social withdrawal
  • Unhappiness and irritability
Signs and tests

A visit to your health care provider will look for other causes of the symptoms and confirm the diagnosis. A psychological evaluation may be needed for more severe depression.

See also: Depression

Support Groups

Expectations (prognosis)

The outcome is good with continuous treatment, although some people have the disorder throughout their lives.

Calling your health care provider

Call for an appointment with your health care provider if you experience symptoms of seasonal affective disorder.


Seasonal affective disorder can sometimes progress to a major depressive syndrome.


As with other types of depression, antidepressant medications and talk therapy can be effective.

Taking long walks during the daylight hours and getting exercise can make the symptoms better. Keep active socially, even if it involves some effort.

Light therapy using a special lamp with a very bright fluorescent light (10,000 lux) to mimic light from the sun may also be helpful.

  • Sit a few feet away from the light box for about 30 minutes every day, preferably in the early morning, to mimic sunrise. An improvement in the symptoms of depression should occur within 3 - 4 weeks if light therapy is going to help.
  • Side effects include eye strain and headache. People who take drugs that make them more sensitive to light, such as certain psoriasis drugs, antibiotics, or antipsychotics, should avoid light therapy. A check-up with your eye doctor is recommended before starting treatment.

Symptoms commonly get better on their own with the change of seasons.


Individuals who have had recurrent seasonal depression should speak with a mental health care professional to explore treatments.


Rohan KJ, Roecklein KA, Tierney Lindsey K, et al. A randomized controlled trial of cognitive-behavioral therapy, light therapy, and their combination for seasonal affective disorder. J Consult Clin Psychol. 2007;75:489-500.

Forms of depression
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Related Taxonomy

Review Date: 2/14/2010
Reviewed By: Fred K. Berger, MD, Addiction and Forensic Psychiatrist, Scripps Memorial Hospital, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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